This invention relates generally to a method and an apparatus for axially aligning a plurality of axially coupled shafts of a steam turbine.
In power plants utilizing steam turbines, a plurality of shafts are axially coupled together. Each shaft carries a plurality of steam turbine blades. High pressure and high temperature steam flowing past these turbine blades experiences an enthalpy change which causes the turbine blades to rotate the shaft. Some power plants include a number of turbines, such as a high pressure turbine, an intermediate pressure turbine, and a low pressure turbine. The various shafts associated with these turbines are axially coupled together and the rotational power developed by each turbine is transmitted to a dynamoelectric machine such as an electromagnetic generator. The generator may also be axially aligned with the shafts. As used herein, the term "axial alignment" is meant to refer to that alignment within certain predetermined tolerances recognized by a person of ordinary skill in the art. In another sense, the term "axially aligned" is meant to refer to items in substantial axial alignment. As recognized by a person of ordinary skill in the art, the axial centerline of a particular steam turbine component varies along the longitudinal aspect of the component due to manufacturing and other design related issues. Therefore, the axial centerline of a steam turbine shaft is within certain tolerances and the axial alignment of two steam turbine shafts must be within the industry recognized standards.
At the initial commissioning of the steam turbine power plant, each turbine shaft is aligned with the other turbine shafts and, if necessary, with the shaft of the electric generator. Each shaft is axially coupled at its outboard end to the adjacent outboard end of another shaft. The axial alignment of the entire system is important due to mechanical considerations as well as efficiency considerations. After a period of time, the steam turbine plant may need refurbishment. At that time, each shaft is axially aligned with the balance of the steam turbine system before recommissioning the system.